PCGamesN.com keeps a list of the top 50 Minecraft world seeds. These seeds include the seed numbers, the version of Minecraft that the seeds work with and screenshots of interesting parts of the worlds contained in each of the seeds.
Minecraft seeds are version dependent, and seeds generally only provide expected results when used with the correct version of Minecraft. Seeds are entered when creating a new world in the game, and they cannot be altered once the world is created. If a seed is not manually entered for a new world creation, Minecraft chooses a random seed to generate the game world instead.